Apparatus to assist a patient&#39;s breathing with a variable ramp period to rise to treatment pressure

ABSTRACT

An apparatus ( 1 ) to assist a patient&#39;s respiration by delivering air to a patient through a mask ( 20 ), including a ramp module ( 10 ) connected to a control unit ( 2 ) to provide the control unit with a pressure value P M  at mask ( 20 ), so that when apparatus ( 1 ) starts functioning, the pressure progressively rises until it reaches a treatment pressure PTi, the apparatus further including a comparator connected to ramp module ( 10 ), at least one device for detecting the patient&#39;s breathing parameters and sending them to the comparator, so that the comparator can determine whether an event (E 1 , E 2  or E 3 ) occurs in patient&#39;s breathing and to send the corresponding data to ramp module ( 10 ) which provides control unit ( 2 ) with a pressure value P M  that will speed up with respect of time, so that the pressure rise at patient&#39;s mask ( 20 ) is accelerated.

This application is a U.S. National Stage of International ApplicationPCT/IB03/01422, filed Mar. 10, 2003, and claims priority of U.S.provisional application Ser. No. 60/362,441, filed Mar. 8, 2002.

TECHNICAL FIELD

This invention concerns the field of apparatus to assist a patientrespiration and more specifically an apparatus bringing progressively tothe pressure of treatment the air the patient is provided with.

BACKGROUND ART

In many treatments apparatus are used to provide patients with air. Morefrequently they are used for patients with a breathing deficiency causedfor example by the weakness of the breathing system or by obstructiveapneas during the sleep. In those cases it is important to control thepressure of the air delivered to the patient. With respiratoryinsufficient patients, apparatus providing air at a higher pressure helpto compensate the weakness of the patients lungs. In the case ofpatients suffering of sleep apneas, providing the air at a higherpressure removes the obstruction of the upper airways.

The pressure of treatment is usually not strong enough to wake thepatient up, but can prevent him from falling asleep. An implementationof treatments apparatus is to wait for the patient to fall asleep beforeproviding air under the treatment pressure. The classical solution is tohave a ramp period, which is a slow increase of the delivered pressurefrom a low level to the treatment pressure.

Still to enhance the comfort of the patient, it is disclosed in patentU.S. Pat. Nos. 5,492,113 and 5,970,975 an apparatus wherein severalcycles of ramp are provided on patient's conscious demand. The cyclesactuated after the first cycle rise faster in pressure. All those rampsare predetermined in shape and duration. The patient can also select afastest shape of ramp or select one special shape in order to fallasleep more easily. This selection being made among differentpredetermined shapes of ramp. However, such devices require from thepatient a minimum of consciousness to activate the ramp cycles. This isnot really very efficient to fall asleep and it is not possible when thepatient has fallen asleep.

Moreover each ramp can not be modified during the time when the ramp isactivated.

SUMMARY OF THE INVENTION

The first object of the invention is to provide a ramp that would beable to modulate automatically, especially when the patient fallsasleep.

A second object of the invention is to provide in any case a maximum oftime in rise of pressure, in order to apply the treatment in any case.

The invention thus concerns an apparatus to assist a patient'srespiration by delivering air to a patient through a mask, comprising:

-   -   a blower to provide the patient with air under a treatment        pressure,    -   a control unit to adjust the pressure delivered by the blower at        the level of the patient's mask,    -   a ramp module connected to the control unit in order to provide        the control unit with the value of pressure P_(M) to settle at        the mask, so that when the apparatus starts functioning, the        pressure progressively rises until the pressure of treatment        P_(T);        the apparatus comprising a comparator connected to the ramp        module, means for detecting the patient's breathing parameters        and sending them to said comparator, in order that in response        to breathing parameters, the comparator is able to determine        that an event occurs in patient's breathing and to send the        corresponding data to the ramp module which provides the control        unit with a value of pressure P_(M) that will speed up with        respect of the time, so that the rise of pressure at patient's        mask is accelerated.

In an implementation of the invention, the value of pressure P_(M) hasalways maximum and/or minimum limits so that the increase of pressure isalso limited in minimum and/or maximum.

Such an apparatus has the advantage to generate a ramp period which canbe modulated in the same ramp, according to patient's breathingparameters.

BRIEF DESCRIPTION OF FIGURES

The purposes, objects and characteristics of the invention will becomemore apparent from the following description when taken in conjunctionwith the accompanying drawings in which:

FIG. 1 represents the apparatus schema,

FIG. 2 represents the pressure delivered to the patient's mask accordingto special events occurring in patient's breathing,

FIG. 3 represents the domain of pressure increase, and

FIG. 4 represents the block diagram for the ramp period.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus according to the present invention is able to generate aramp period which can be modulated in respect of the time required bythe patient for falling asleep.

The apparatus as represented in FIG. 1 comprises a blower 4 to providethe patient with air. This blower is connected to a tube 8 on a firstextremity, the second extremity being connected to the mask 20 whereinthe patient breathes. A control unit 2 provides the blower 4 with theelectrical control required to enable the blower to function in order toset a given pressure at the patient's mask or blower's outlet. Thispressure could be measured by a pressure transducer 6 at the mask levelor at the tube extremity, which is connected to the mask. A ramp module10 is connected to the control unit 2 and to the pressure transducer 6.The ramp module provides the control unit 2 with the pressure at thepatient's mask and with the pressure to settle at the patient's mask atthe starting of the apparatus 1 functioning. During the treatment thecontrol unit 2 is able to detect breathing events according to thepressure sensor 6 or any other way to evaluate or measure the patient'sairflow. Such detection can be given by airflow sensors which providethe control unit with ressure parameters, the control units being thusable to detect that an event is occurring.

The apparatus according to the present invention is able to modulate therise in pressure during one single ramp period, which is impossible toperform for apparatus of prior art. The apparatus comprises a rampmodule 10 connected to the control unit 2 in order to provide thecontrol unit with the value of pressure P_(M) to settle at the patient'smask, so that when said apparatus starts functioning, the pressureprogressively rises until the pressure of treatment P_(T). The apparatuscomprises a comparator which is not represented in FIG. 1 and that canbe comprised in the control unit 2. This comparator is connected to theramp module 10. The apparatus comprise also at least one means fordetecting the patients breathing parameters and sending them to saidcomparator, in order that in response to said breathing parameters, thecomparator is able to determine that an event occurs in patientbreathing and to send the corresponding data to the ramp module whichprovide the control unit 2 with a value of pressure P_(M) that willspeed up in respect of the time, so that the rise of pressure atpatient's mask is accelerated.

According to a preferred embodiment, the ramp module 10 provides thevalue of pressure P_(M) being a linear function of time wherein theincrease coefficient K_(RP) is constant, said ramp module increasingthat coefficient of a constant value K_(E) when the control unit 2 senda data corresponding to the event which occurred.

In the apparatus 1 according to the present invention, a minimum speedof rise in pressure until the treatment pressure is set, as representedby the curve C₂ on FIG. 3. This minimum rise of pressure in respect oftime is called in the present application a safety ramp C₂. Before theramps period starts at the instant t_(S), a minimum starting pressure P₀is delivered. After the instant t_(S), even if the patient is notasleep, the pressure at the mask will start rising. In any case at theinstant t_(T), the treatment pressure will be reached; this means thatthe curve C2 represents the minimum speed of rise in pressure. In apreferential implementation of the invention, the minimum speed of risein pressure is proportional to time, the coefficient to rise in pressureaccording to time being K_(SR). Also it can be set a maximum of rise inpressure as represented by the curve C₁ on FIG. 3. The maximum of risein pressure can also be given a linear function of time. Between thesetwo limits the rising of the pressure can be modulated by the controlunit 2 in respect of the patient's falling asleep. That is to say thatwhenever any events occurs or not, the pressure provided at thepatient's mask P_(PM) before the time of plain treatment t_(T) will becomprised between these two limits, this domain of pressure variationsbeing represented in FIG. 3 by the hachures.

When a patient is asleep his respiration becomes stable, this is used todetect the instant when the patient falls asleep. Another way to detectwhen the patient falls asleep is to detect the drop of frequency betweenthe awake rate breathing and the awake breathing. As represented in FIG.4 and according to a preferential implementation, the control unit 2transmits to the ramp module an output average pressure value P_(M)which is the pressure value required to be delivered to the patient'smask. When the patient is about to fall asleep, his respiration becomesstable. In that case the P_(M) value is increased, preferentially as alinear function of time, the proportional coefficient being K_(RP). Ifthe pressure value P_(M) is inferior to the safety ramp pressure S_(RP),the pressure P_(M) is set to the value of the safety ramp pressureS_(RP), which is in a preferential implementation calculated by the rampmodule 10 by multiplying the time spent from the beginning of the ramproutine to the present time by the coefficient K_(SP). When the pressurevalue P_(M) equals or is superior to the treatment pressure P_(T), theP_(M) pressure is maintained equal to the treatment pressure valueP_(T). On the contrary the control unit 2 checks again if therespiration is stable. This shows that until the patient falls asleepthe P_(M) value will not be superior to the treatment pressure P_(T),and will only equal it when the patient falls asleep or when the safetyramp reaches the treatment pressure value. This also shows that duringthe ramp period, if the respiration is stable, the air provided can risefaster than the safety ramp. In that case, the coefficient K_(RP) willbe higher than the coefficient K_(SP). The ramp module will thus enableto the control unit to accelerate the rise in pressure when the patientsfall asleep and when no events are detected.

Another implementation of the apparatus according to the presentinvention is that when the control unit detects an event in patientsbreathing that shows an asleep state, the control unit will provide theramp module 10 with the information. The ramp module will thus increaseagain the rise in pressure.

The following are examples of ramp periods generated by the apparatusaccording the present invention.

EXAMPLE 1 Variations of Value P_(M) According to Different Events

FIG. 2 represents one example of the apparatus functioning wherein threesystems of coordinates are represented: pressure value PM as a functionof time, patient's breathing B as a function of time and snoring S as afunction of time. At a time t_(S), the ramp module 10 activates the risein pressure. At time t₁ as a slowdown E₁ in breathing is detected, therise in pressure is accelerated by the ramp module 10. Then at time t₂snoring E₂ is detected. Thus, the rise in pressure is accelerated againby the ramp module. As at time t₃ a snoring E₃ is still detected theramp module still accelerates the rise in pressure. As represented onFIG. 2, the preferred embodiment is a linear rise in pressure. Thus attime t_(S), the coefficient K_(RP) of rise in pressure is constant. Eachtime an event is detected the module ramp adds a given constant valueK_(E) to this coefficient, the slope of the linear function being thusaccentuated at each event. This will last until the treatment pressureP_(T) is raised. Then the ramp is completed and the control unit appliesthe treatment pressure to the patient's mask. The value K_(E) can be setby the physician in a non volatile memory and can be different accordingto the event detected.

EXAMPLE 2 Example of Calculating the Value P_(M)

In this example the treatment pressure P_(T) is of 10 hecto pascal(hPa). The initial pressure P₀ of the air provided at patient's mask is4 hPa. A physician has set that the ramp will start at a time ts of 2minutes and has set the initial coefficient K_(RP) at 0.2 hPa per minute(hPa/mn). The physician also set that when a snoring is detected K_(E)equals 1 hPa when the breath rate is below a set threshold.

When the apparatus starts the control units supply the blower in orderto set at the patient's mask a pressure of 4 hPa. After 2 minutes, theramp module starts increasing the value P_(M). As no events occurs, thecoefficient K_(RP) stays at 0.2 hPa. After 10 minutes the value P_(M) isof 5.6 hPa (8 minutes multiplied by 0.2 hPa/mn and added to the 4 hPa).After these ten minutes, the patient's breath is below threshold. Theramp module adds the corresponding K_(E) value to the coefficientK_(RP), which thus equals 1.2 hPa/mn. The treatment pressure is thusraised in about 13 minutes and 40 seconds.

1. An apparatus to assist a patient's respiration by delivering air to apatient through a mask, comprising: a blower to provide the patient withair under a treatment pressure; a control unit to adjust the pressuredelivered by said blower at the level of said mask; a ramp moduleconnected to the control unit in order to provide the control unit witha value of pressure P_(M) to settle at said mask so that, when saidapparatus starts functioning, the pressure progressively rises until thepressure of treatment P_(T), the rise of pressure until the pressure oftreatment P_(T) corresponding to a ramp period; a comparator connectedto the ramp module; and at least one means for detecting the patient'sbreathing parameters during said ramp period and sending them to saidcomparator such that the comparator is able during this said ramp periodto determine whether an event (E₁, E₂ or E₃) occurs in patient'sbreathing based on said breathing parameters and to send thecorresponding data to the ramp module which provides the control unitwith a value of pressure P_(M) that will speed up with respect of timeduring this said ramp period, in order to accelerate the rise ofpressure at patient's mask within the same said ramp period.
 2. Theapparatus according to claim 1, wherein said ramp module provides thevalue of pressure P_(M) being a linear function of time wherein anincrease coefficient K_(RP) is constant, said ramp module increasingthat coefficient of a constant value K_(E) when the control unit sends adata corresponding to said event (E₁, E₂ or E₃).
 3. The apparatusaccording to claim 1, wherein the value of pressure P_(M) has alwaysmaximum and/or minimum limits so that the increase of pressure is alsolimited in minimum and/or maximum.
 4. The apparatus according to claim2, wherein said ramp module comprises a memory where a minimumcoefficient K_(SRP) is stored, said ramp module always maintaining thecoefficient K_(SRP) equal or greater than said minimum coefficientK_(SRP), so that the ramp module provides the control unit with a valueof pressure P_(M) always greater than a minimum limit.
 5. The apparatusaccording to claim 2, wherein said ramp module comprises a memory wherea maximum coefficient K_(MRP) is stored, said ramp module alwaysmaintaining the coefficient K_(RP) equal or less than said maximumcoefficient K_(MRP), so that the ramp module provides the control unitwith a value of pressure P_(M) always less than a maximum limit.
 6. Theapparatus according to claim 1, wherein said means for detecting thepatient's breathing parameters enable the control unit to compute theairflow at patient's mask, said comparator determining whether an event(E₁, E₂ or E₃) is occurring with the airflow parameters or shape.
 7. Theapparatus according to claim 1, wherein the ramp module increases thevalue of pressure P_(M) when an anomaly in patient's breathing isdetected.
 8. The apparatus of claim 7, wherein said anomaly is eithersnoring or apnea.
 9. The apparatus according to claim 1, wherein theramp module increases the value of pressure P_(M) when the patient'sbreathing parameters correspond to a drop between awake breathing andasleep breathing or when they correspond to a stable frequency ofbreathing.